Dynamics of Avirulence Genes and Races in the Population of Magnaporthe oryzae in Jilin Province, China

Rice blast, caused by Magnaporthe oryzae, is a devastating global disease. Its control through the deployment of host resistance genes relies on a detailed knowledge of the pathogen’s race structure and the corresponding avirulence (Avr) genes. To guide effective rice breeding for blast resistance, this study investigated the population dynamics of M. oryzae in Jilin Province from 2022 to 2024. The distribution frequencies of seven Avr genes were detected using PCR and Avr gene-specific primers, and the physiological race structure of 193 isolates was characterized using a set of Chinese differential cultivars, which contains seven cultivars. The results revealed a high prevalence and stability of specific Avr genes, with Avr-Pi9, Avr-Pias, Avr-Piz-t, and Avr-Pib all exhibiting detection frequencies exceeding 80%. In particular, Avr-Pib showed a high frequency (80.83%) and a very low disease incidence (0.64%) on the differential variety Sifeng 43 (which carries Pib), confirming its low mutation rate and the ongoing effectiveness of the corresponding resistance gene. Conversely, the significant decline in Avr-co39 suggests that its corresponding resistance gene should be avoided. Race diversity increased over the three-year period, characterized by a shift toward a more complex structure dominated by ZG1, ZA17, ZA43, and ZB31. Based on the gene-for-gene interactions and pathogen population structure, we recommend a breeding strategy that prioritizes the incorporation of the highly effective Pib, Pi54, and Pik genes, utilizing resistant donors like Sifeng 43. These results can help inform the design of sustainable management strategies adapted to the changing pathogen population.